The present invention relates generally to the developer of an electrostatic reproduction machine, but more particularly to improved means for periodically emptying developing material from a discharge opening in the developer, and means for counting the number of times the discharge opening has been opened.
In conventional xerography, a xerographic plate comprising a layer of photosensitive insulating material affixed to a conductive backing is used to support electrostatic latent images. In the xerographic process, the photosensitive surface is electrostatically charged, and the charged surface is then exposed to a light pattern of the image being reproduced to thereby discharge the surface in the areas where light strikes the surface. The undischarged areas of the surface thus form an electrostatic charge pattern (an electrostatic latent image) conforming to the original pattern. The latent image is then developed by contacting it with a finely divided electrostatically attractable powder referred to as "toner". Toner is held on the image areas by the electrostatic charge on the surface. Where the charge is greater, a greater amount of toner is deposited. Thus, a toner image is produced in conformity with a light image of the copy being reproduced. Generally, the developed image is then transferred to a suitable transfer member (e.g., paper), and the image is affixed thereto to form a permanent record of the original document.
In practice of xerography, the transfer member is caused to move in synchronized contact with the photosensitive surface during the transfer operation, and an electrical potential opposite from the polarity of the toner is applied to the side of the paper remote from the photosensitive surface to electrostatically attract the toner image from the surface to the paper.
In a prior art developer it was necessary to entirely remove the dump door in order to empty the developing material. Because the door was on the bottom of the developer and near the very bottom of the machine, a key operator had to get down on his or her hands and knees to remove the door. A clamp was removed from the end of the door nearest the key operator, and the door was pulled toward the operator so as to pull two tabs on the other end of the door out of corresponding openings in the developer wall, thus causing the door and the developing material to drop into a receptacle placed beneath the developer. There were at least three problems with this arrangement. First, the key operator had to brush toner off the door before replacing it which meant the operator's hands and clothing often got quite dirty. The second problem was that the door was difficult to replace since the operator had to align the two tabs with the corresponding openings in the developer wall in the rear of the reproduction machine. The third problem was related to the second and that was the possibility that the operator might get his or her fingers caught in a paddle wheel located within the developing apparatus just above the dump door when attempting to replace the door.
Another problem with prior art developers was that there was no way of correlating the copy count with the number of times the dump door had been opened to empty the developing material. Since the manufacturer of the developing material often warrants that the material will last for a certain number of copies, it is desirable that he be able to determine this correlation.
Thus, what is needed is an improved means for emptying developing material from a discharge opening in the developer and means for indicating the number of times that the discharge opening has been opened. The emptying means should also have a minimum number of parts and be easy to mount over the existing discharge opening of the developer housing.